The present disclosure discloses a method of forming a semiconductor layer on a substrate. The method includes patterning the semiconductor layer into a fin structure. The method includes forming a gate dielectric layer and a gate electrode layer over the fin structure. The method includes patterning the gate dielectric layer and the gate electrode layer to form a gate structure in a manner so that the gate structure wraps around a portion of the fin structure. The method includes performing a plurality of implantation processes to form source/drain regions in the fin structure. The plurality of implantation processes are carried out in a manner so that a doping profile across the fin structure is non-uniform, and a first region of the portion of the fin structure that is wrapped around by the gate structure has a lower doping concentration level than other regions of the fin structure.
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7. A method comprising:
forming a fin structure over a semiconductor substrate;
forming a gate structure over the fin structure such that the gate structure at least partially wraps around the fin structure;
forming a first doped region having a dopant type at a first concentration in the fin structure, wherein the first doped region is formed under the gate structure;
forming a second doped region having the dopant type at a second concentration that is different than the first concentration in the fin structure, wherein the second doped region extends laterally within the fin structure from the first doped region under the gate structure to under a spacer on a sidewall of the gate structure; and
forming a third doped region having the dopant type at a third concentration that is different than the second concentration in the fin structure, wherein the third doped region extends laterally within the fin structure from the second doped region under the spacer to beyond an outer edge of the spacer away from the gate structure, wherein the dopant type of the first, second, and third doped regions is the same.
13. A method comprising:
forming a semiconductor layer over a substrate;
forming a first doped region having a dopant type at a first concentration in the semiconductor layer;
patterning the semiconductor layer into a fin structure, wherein the fin structure includes the first doped region;
forming a gate structure over the fin structure such that the gate structure at least partially wraps around the fin structure;
forming a second doped region having the dopant type at a second concentration that is different than the first concentration in the fin structure, wherein the second doped region extends laterally within the fin structure from the first doped region under the gate structure to under a spacer on a sidewall of the gate structure; and
forming a third doped region having the dopant type at a third concentration that is different than the second concentration in the fin structure, wherein the third doped region extends laterally within the fin structure from the second doped region under the spacer to beyond an outer edge of the spacer away from the gate structure, wherein the dopant type of the first, second, and third doped regions is the same.
1. A method of fabricating a semiconductor device, comprising:
forming a semiconductor layer on a substrate;
patterning the semiconductor layer into a fin structure;
forming a gate dielectric layer and a gate electrode layer over the fin structure;
patterning the gate dielectric layer and the gate electrode layer to form a gate structure in a manner so that the gate structure wraps around a portion of the fin structure; and
performing a plurality of implantation processes to form source/drain regions in the fin structure, the plurality of implantation processes being carried out in a manner so that a doping profile across the fin structure is non-uniform including a first region having a first doping concentration level, a second region extending from the first region and partially wrapped around by the gate structure and having a second doping concentration level that is different than the first doping concentration level, and a third region extending from the second region but not wrapped around by the gate structure and having a third doping concentration level that is different than the second doping concentration level, wherein the first, second, and third regions all have the same doping polarity.
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wherein the second doped region is a lightly doped source/drain region associated with the gate structure, and
wherein the third doped region is a source/drain region associated with the gate structure.
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This application is a divisional application of U.S. application Ser. No. 13/077,144, filed Mar. 31, 2011 which claims priority to U.S. Application No. 61/434,963, filed on Jan. 21, 2011, entitled “Non-Uniform Channel Junction-Less Transistor,” the entire disclosures of which are incorporated herein by reference.
The semiconductor industry has progressed into nanometer technology process nodes in pursuit of higher device density, higher performance, and lower costs. As this progression takes place, challenges from both fabrication and design issues have resulted in the development of three-dimensional designs, such as fin-like field effect transistor (FinFET) device. A typical FinFET device is fabricated with a thin “fin” (or fin-like structure) extending from a substrate. The fin usually includes silicon and forms the body of the transistor device. The channel of the transistor is formed in this vertical fin. A gate is provided over (e.g., wrapping around) the fin. This type of gate allows greater control of the channel. Other advantages of FinFET devices include reduced short channel effect and higher current flow. However, for conventional FinFET devices, the amount of drain current of FinFET devices may be adversely impacted by high parasitic resistance.
Therefore, while existing methods of fabricating FinFET devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect.
The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
It is understood that the following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the sake of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, various features may be arbitrarily drawn in different scales for the sake of simplicity and clarity.
The use of FinFET devices has been gaining popularity in the semiconductor industry. Referring to
FinFET devices offer several advantages over traditional Metal-Oxide Semiconductor Field Effect Transistor (MOSFET) devices (also referred to as planar devices). These advantages may include better chip area efficiency, improved carrier mobility, and fabrication processing that is compatible with the fabrication processing of planar devices. Thus, it may be desirable to design an integrated circuit (IC) chip using FinFET devices for a portion of, or the entire IC chip.
However, traditional FinFET devices may have an uniform channel profile and thus may suffer from high parasitic resistance, which may adversely affect the magnitude of the drain current. Here, the various aspects of the present disclosure involve forming a FinFET device having a non-uniform channel profile and consequently has a reduced parasitic resistance. Therefore, the FinFET device fabricated according to the present disclosure has improved drain current performance. The following Figures illustrate various cross-sectional views and top views of a FinFET device at different stages of fabrication. For the sake of clarity, three-dimensional axes X, Y, and Z are shown in
Referring now to
A semiconductor layer 130 is formed on the substrate 110. In an embodiment, the semiconductor layer 130 includes a crystal silicon material. It is understood that the semiconductor layer 130 may include other suitable materials in alternative embodiments. An implantation process 140 is performed on the semiconductor layer 130 to implant a plurality of dopant ions to the semiconductor layer 130. The dopant ions include an N-type material in an embodiment, for example arsenic (As) or phosphorous (P). After the implantation process 140 is performed, a doping concentration level is in a range from about 1×1017 ions/cm3 to about 5×1019 ions/cm3. In other embodiments, the dopant ions may include a P-type material, for example boron (B), and the doping concentration levels may be different.
Referring now to
Referring now to
Referring now to
After the gate structure 200 is formed, an implantation process 220 is performed to implant dopant ions into portion of the fin structure 150 (the patterned-semiconductor layer 130) located on either (or opposite) side of the gate structure 200, thereby forming source/drain regions 230-231. The dopant ions have the same doping polarity as the dopant ions used in the implantation process 140. For example, in an embodiment where an N-type dopant is used for the implantation process 140, an N-type dopant is used for the implantation process 220 as well. In an embodiment, the implantation process 220 has a higher dosage than the implantation process 140, and consequently the doping concentration level of the source/drain regions 230-231 is higher than that of the channel region 205 (portion of the fin structure 150 being wrapped around by the gate structure 200). In an embodiment, the doping concentration level of the source/drain regions 230-231 is in a range from about 1×1018 ions/cm3 to about 1×1020 ions/cm3.
Referring now to
After the spacers 240-241 are formed, an implantation process 260 is performed to implant dopant ions into portion of the fin structure 150 not covered by the spacers 240-241 or the gate structure 200. This implantation process 260 is part of the formation process of the source/drain regions 230-231. The dopant ions have the same doping polarity as the dopant ions used in the implantation processes 140 and 220. For example, in an embodiment where an N-type dopant is used for the implantation processes 140 and 220, an N-type dopant is used for the implantation process 260 as well. In an embodiment, the implantation process 260 has a higher dosage than the implantation process 220, and consequently the doping concentration level of the source/drain regions 230-231 not underneath the spacers 240-241 is higher than that of the source/drain regions underneath the spacers 240-241. In an embodiment, the doping concentration level of the portions of the source/drain regions 230-231 not covered by the gate structure 200 or the spacers 240-241 is in a range from about 1×1020 ions/cm3 to about 1×1021 ions/cm3.
It is understood that an epitaxial growth process may replace the implantation process 260 in an alternative embodiment. Furthermore, an activation annealing process may be subsequently performed, which may have a temperature range from about 900 degrees Celsius to about 1050 degrees Celsius, and a process duration of less than about 1 second.
Based on the discussions above, it can be seen that the fin structure 150 has a non-uniform doping concentration profile. Due to the various implantation processes discussed above, the doping concentration levels decrease (although not necessarily linearly) as it gets closer to the center directly beneath the gate structure 200. For the purposes of providing a clearer illustration,
Referring to
The region N0 has a width 270, the region N1 has a width 280, and the region N1 has an overlapping distance 290 with the gate 200. The widths 270-280 and the distance 290 are all measured in the X direction. In an embodiment, the width 270 is in a range from about ¼ to about ⅞ of the width 210 (also shown in
In an embodiment, the doping concentration level of the region N0 is less than about 2×1018 ions/cm3. In an embodiment, the doping concentration level of the region N1 is greater than about 1×1019 ions/cm3. In an embodiment, the doping concentration level of the region N2 is greater than about 1×1020 ions/cm3.
A complementary metal oxide semiconductor (CMOS) device implemented according to various aspects of the present disclosure can have both n-FETs and p-FETs on the same chip. For the n-FETs, the work function of the gate structure is closer to the conduction band edge. For the p-FETs, the work function of the gate structure is closer to the valence band edge.
The approximate boundaries of the N0, N1, and N2 regions discussed above are also illustrated in
Although the doping concentration level changes, the dopant polarity remains the same across all three of the regions N0, N1, and N2. In one embodiment, all three regions N0, N1, and N2 are N-type doped. In another embodiment, all three regions N0, N1, and N2 are P-type doped.
The gate length Lg of the FinFET device is also shown in
Referring to
Referring now to
Referring now to
Table 1 below lists some of the differences between some of the embodiments of the present disclosure and other devices. These other devices may include traditional FinFET devices, or traditional junction-less transistors, and modified junction-less transistors. It is understood that the differences in Table 1 are merely examples and are not meant to be limiting. Additional differences may exist but are not listed in Table for the sake of simplicity.
TABLE 1
Certain
Traditional
Modified
embodiments of
Traditional
junction-less
junction-less
present disclosure
FinFET devices
transistors
transistors
Work
N-type
N-type
P-type
P-type
function
(4.1 V~4.65 V)
Channel
N−
P−
N
N−
LDD
N+
N+
none
N+
S/D
N++
N++
N++
N++
According to Table 1, some of the embodiments of the present disclosure have:
a N-type work function tuned in the range from about 4.1 volts to about 4.65 volts;
an N-type channel that has a low doping concentration level;
an N-type LDD region that has a heavier doping concentration level than the channel; and
an N-type S/D region that has a heavier doping concentration level than the LDD region.
The above combination of properties are not found in any of the other devices. For example, the traditional FinFET devices have an oppositely doped channel, the traditional junction-less transistors have a doping concentration level higher than that of the embodiments herein and an LDD region that is not doped. Other differences can be identified by referring to Table 1 above.
It is understood that although the Figures discussed above only show a single FinFET device, a plurality of similar FinFET devices may be fabricated on a single wafer or on the same chip. For example, a complementary metal oxide semiconductor (CMOS) device includes both n-FET devices and p-FET devices. Both the n-FET devices and the p-FET devices can be fabricated using the process flow discussed above. In an embodiment, a work function of the gate of an n-FET device is closer to a conduction band edge, and a work function of the gate of a p-FET device is closer to a valence band edge.
The various embodiments of the present disclosure discussed herein offer several advantages, it being understood that other embodiments may offer different advantages, and that no particular advantage is required for any embodiment. One advantage of having such a non-uniform doping profile across the fin structure 150 is reduced parasitic resistance and therefore increased drain current over conventional devices. In some embodiments, the drain current can be increased by at least 20% while leakage current and channel dose are comparable with conventional devices.
One of the broader forms of the present disclosure involves a semiconductor device. The semiconductor device includes: a semiconductor layer disposed over a substrate, the semiconductor layer having a fin structure; a gate structure disposed over the fin structure, the gate structure having a gate dielectric layer and a gate electrode layer, the gate structure wrapping around a portion of the fin structure; and source/drain regions disposed in the fin structure; wherein a doping profile across the fin structure is non-uniform, and wherein a first region of the portion of the fin structure being wrapped around by the gate structure has a lower doping concentration level than the rest of the fin structure.
Another one of the broader forms of the present disclosure involves a FinFET semiconductor device. The FinFET semiconductor device includes: a fin structure formed over a substrate, the substrate including one of: a silicon material and an insulator material; a gate formed in a manner such that it at least partially wraps around a segment of the fin structure; and source/drain regions formed in the fin structure; wherein: the fin structure includes a first portion, a second portion, and a third portion; the first portion is completely wrapped around by the gate; the second portion is at least partially wrapped around by the gate and has a heavier doping concentration level than the first portion; and the third portion is not wrapped around by the gate and has a heavier doping concentration level than second portion.
Yet another one of the broader forms of the present disclosure involves a method of fabricating a semiconductor device. The method includes: forming a semiconductor layer on a substrate; patterning the semiconductor layer into a fin structure; forming a gate dielectric layer and a gate electrode layer over the fin structure; patterning the gate dielectric layer and the gate electrode layer to form a gate structure in a manner so that the gate structure wraps around a portion of the fin structure; and performing a plurality of implantation processes to form source/drain regions in the fin structure, the plurality of implantation processes being carried out in a manner so that a doping profile across the fin structure is non-uniform, and wherein a first region of the portion of the fin structure being wrapped around by the gate structure has a lower doping concentration level than other regions of the fin structure.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
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